An optical wavelength-division multiplexed (WDM) system uses a single fiber link to simultaneously transmit optical signals at different carrier wavelengths. Dense WDM (DWDM) techniques have been used to increase the number of multiplexed wavelengths in a WDM fiber link by reducing the wavelength spacing between two adjacent wavelengths. Such WDM and DWDM systems use multiple lasers at different WDM wavelengths to produce the optical carriers.
It is desirable to stabilize the laser wavelengths of the multiple lasers at their respective, pre-selected WEM wavelengths. One standard for the WDM wavelengths is established by the International Telecommunications Union (ITU) in which the separation between two adjacent communication channels is 0.8 nm, or 100 GHz in frequency. Thus, the lasers for WDM systems should have narrow output linewidths at those ITU WDM wavelengths. In addition, the wavelength of each WDM laser should be stable to avoid drifting into the wavelength range allocated for an adjacent channel.
A wavelength control system, e.g., a wavelocker, may be used to control the output laser wavelength of a laser. Such a system may include a detection unit to measure the variation of the output laser wavelength from a desired laser wavelength and a locking mechanism to adjust the laser by negating the variation so that the output laser wavelength is locked at the desired laser wavelength.